The type I interleukin-1 receptor (IL-1RI) mediates the biological effects of interleukin-1, a pro-inflammatory cytokine (Sims et al., Science 241:585-589, 1988; Curtis et al., Proc. Natl. Acad. Sci. USA 86:3045-3049, 1989). A second interleukin-1 receptor (designated type II IL-1R or IL-1RII) binds IL-1, but does not appear to mediate signal transduction (McMahan et al., EMBO J. 10:2821, 1991; Sims et al., Proc. NatL Acad. Sci. USA 90:6155-6159,1993). IL-1RI and IL-1RII each bind IL-1xcex1 and IL-1xcex2.
IL-1RI and IL-1RII belong to a family of proteins that exhibit significant sequence homology. One such protein is IL-1R accessory protein (IL-1R AcP), described in Greenfeder et al. (J. BioL Chem. 270:13757-13765, 1995). This protein, by itself, is not capable of binding IL-1, but does form a complex with IL-1RI and either IL-1xcex1 and IL-1xcex2. When co-expressed with IL-1RI, recombinant IL-1R AcP increases the binding affinity of IL-1RI for IL-1xcex2 (Greenfeder et al., supra).
The protein variously known as ST2, ST2L, T1, or Fit-1 also is a member of the IL-1R family, but does not bind IL-1. Cloning of mouse and rat cDNAs encoding membrane-bound and secreted forms of this protein has been reported (Klemenz et al., Proc. NatL Acad. Sci. USA 86:5708, 1989; Tominaga, FEBS LETTERS 258:301, 1989; Yanagisawa et al., FEBS LETTERS 318:83, 1993; Bergers et al., EMBO J. 13:1176, 1994). Human ST2 cDNA and genomic clones have been isolated as well (Tominaga et al. Biochimica et Biophysica Acta 1171:215, 1992).
Other proteins exhibiting significant sequence homology with IL-1RI are murine MyD88 (Lord et al., Oncogene 5: 1095-1097, 1990), human rsc786 (Nomura et al., DNA Res. 1:27-35, 1994), and a number of Drosophila proteins, the best characterized of which is Toll (Hashimoto et al., Cell 52, 269-279, 1988). The tobacco N gene (Whitham et al., Cell 78:1101-1115, 1994) is among the additional IL-1R family members.
MyD88, rsc786, Toll, and the tobacco N gene product contain domains exhibiting significant homology to the cytoplasmic domain of the IL-1RI. The IL-1R AcP and ST2 proteins exhibit sequence similarity to IL-1RI in both their extracellular and cytoplasmic portions. The B16R protein of vaccinia virus (Goebel et al., Virology 179:247, 1990) appears to be a viral homolog of IL-1RII.
Identification of additional receptors of this family is desirable. Such receptor proteins can be studied to determine whether or not they bind IL- 1, and, if so, whether the receptors play a role in mediating signal transduction. The possible existence of additional affinity-converting subunits for receptors of this family can be explored, as well.
The present invention provides a novel receptor protein designated 2F1. Both soluble and membrane-bound forms of 2F1 are disclosed herein. The present invention also provides isolated DNA encoding 2F1 proteins, expression vectors comprising the isolated DNA, and a method for producing 2F1 by cultivating host cells transformed with the expression vectors under conditions appropriate for expression of the 2F1 protein. Antibodies directed against 2F1 are also disclosed. 2F1 finds use in inhibiting prostaglandin synthesis and alleviating inflammation.
DNA encoding a novel receptor protein designated 2F1 has been isolated in accordance with the present invention. Expression vectors comprising the 2F1 DNA are provided, as well as methods for producing recombinant 2F1 polypeptides by culuring host cells containing the expression vectors under conditions appropriate for expression of 2F1, then recovering the expressed 2F1 protein. Purified 2F1 protein is also encompassed by the present invention, including soluble forms of the protein comprising the extracellular domain.
The present invention also provides 2F1 and immunogenic fragments thereof that may be employed as immunogens to generate antibodies specific thereto. In one embodiment, the antibodies are monoclonal antibodies.
Human 2F1 clones were isolated as described in example 1. A human 2F1 DNA sequence is presented in SEQ ID NO:1, and the amino acid sequence encoded thereby is presented in SEQ ID NO:2. The protein includes a signal peptide (amino acids xe2x88x9219 to xe2x88x921) followed by an extracellular domain (amino acids 1 to 310), a transmembrane region (amino acids 311 to 332), and a cytoplasmic domain (amino acids 333 to 522).
Mouse 2F1 cDNA was isolated by cross-species hybridization, as described in example 2. The DNA and encoded amino acid sequences of this mouse 2F1 DNA are presented in SEQ ID NO:3 and SEQ ID NO:4. The protein of SEQ ID NO:4 comprises a signal peptide (amino acids xe2x88x9218 to xe2x88x921), an extracellular domain (amino acids 1 to 307), a transmembrane region (amino acids 308 to 330), and a cytoplasmic domain (amino acids 331 to 519). The mouse and human 2F1 amino acid sequences are 65% identical.
The amino acid sequence of the 2F1 protein indicates that it is a member of the IL-1receptor family. Of the known IL-1 receptor family members, 2F1 has the highest degree of sequence homology with IL-1R accessory protein (IL-1R AcP), T1/ST2, and type I IL-1 receptor (IL-1RI). The murine 2F1 amino acid sequence of SEQ ID NO:4 is 31% identical to the amino acid sequence of murine IL-1R AcP, 30% identical to that of the full length murine T1/ST2, and 27% identical to that of the murine IL-1RI. The cytoplasmic domains show slightly greater sequence conservation (36%-44%) than do the extracellular portions (20%-27%).
The binding assay described in example 3 was conducted to determine whether 2F1 binds IL-1xcex1, IL-1xcex2, or IL-1 receptor antagonist. Although 2F1 is a member of the IL-1 receptor family, it did not bind any of the three proteins tested.
Human and mouse 2F1are within the scope of the present invention, as are 2F1 proteins derived from other organisms, including but not limited to mammalian species such as rat, bovine, porcine, or various non-human primates. DNA encoding 2F1 proteins from additional organisms can be identified by cross-species hybridization techniques. Messenger RNAs isolated from various cell types can be screened in Northern blots to determine a suitable source of MRNA for use in cloning 2F1 cDNA from other species.
The term xe2x80x9c2F1xe2x80x9d as used herein refers to a genus of polypeptides that are substantially homologous to a native 2F1 protein (e.g., the protein of SEQ ID NO:2 or 4), and which exhibit a biological activity of a native 2F1 protein. 2F1 proteins of the present invention include membrane-bound proteins (comprising an extracellular domain, a transmembrane region, and a cytoplasmic domain) as well as truncated proteins that retain a desired property. Such truncated proteins include, for example, soluble 2F1 comprising only the extracellular domain or a fragment thereof. Also included are variants of native 2F1 proteins, wherein the variants retain a desired biological activity of a native 2F1. Such variants are described in more detail below.
A 2F1 polypeptide, or fragment or variant thereof, can be tested for biological activity in any suitable assay. When the cytoplasmic domain is altered (e.g., truncated, or altered by deletion, addition, or substitution of amino acid residues), the 2F1 polypeptide can be tested for biological activity in a signal transduction assay. Such assays include, but are not limited to, those described in examples 5 to 7 below. The altered cytoplasmic domain can be fused to the extracellular domain of an IL-1 receptor, and the resulting chimeric receptor tested for the ability to respond to IL-1 by NF-xcexaB activation (see the procedure in example 5), induction of IL-8 promoter function (example 6), or stimulation of prostaglandin E2 synthesis (example 7). 2F1 polypeptides that include an extracellular domain (e.g., soluble 2F1, as described below) can be tested for the ability to inhibit prostaglandin E2 synthesis in vivo in animal studies. The 2F1 is administered in vivo, and prostaglandin E2 levels in the animals are measured (before and after administration of 2F1, and compared to control animals) by any suitable means, e.g., by ELISA.
One embodiment of the present invention is directed to soluble 2F1 polypeptides. Soluble 2F1 polypeptides comprise all or part of the extracellular domain of a native 2F1, but lack the transmembrane region that would cause retention of the polypeptide on a cell membrane. When initially synthesized, soluble 2F1 polypeptides advantageously comprise the native (or a heterologous) signal peptide to promote secretion, but the signal peptide is cleaved upon secretion of 2F1 from the cell.
One use of soluble 2F1 polypeptides is in blocking a biological activity of 2F1. Soluble 2F1 may be administered to a mammal to bind any endogenous 2F1 ligand(s), thereby inhibiting the binding of such ligands to endogenous receptors comprising 2F1. In one embodiment, a soluble 2F1 polypeptide is administered to treat pain or inflammation by inhibiting prostaglandin synthesis, as discussed in more detail below.
Soluble 2F1 may be identified (and distinguished from its non-soluble membrane-bound counterparts) by separating intact cells which express the desired protein from the culture medium, e.g., by centrifugation, and assaying the medium (supernatant) for the presence of the desired protein. The presence of 2F1 in the medium indicates that the protein was secreted from the cells and thus is a soluble form of the desired protein. Soluble 2F1 may be a naturally-occurring form of this protein.
The use of soluble forms of 2F1 is advantageous for certain applications. Purification of the proteins from recombinant host cells is facilitated, since the soluble proteins are secreted from the cells. Further, soluble proteins are generally more suitable for intravenous administration.
Examples of soluble 2F1 polypeptides include those comprising the entire extracellular domain of a native 2F1 protein. One such polypeptide is a soluble human 2F1 comprising amino acids 1 through 310 of SEQ ID NO:2. Another is a soluble murine 2F1 comprising amino acids 1 through 307 of SEQ ID NO:4. When initially expressed within a host cell, the soluble polypeptide may additionally comprise one of the heterologous signal peptides described below that is functional within the host cells employed. Alternatively, the polypeptide may comprise the native signal peptide, such that the 2F1 comprises amino acids xe2x88x9219 through 310 of SEQ ID NO:2 or amino acids xe2x88x9218 through 307 of SEQ ID NO:4. Soluble 2F1 polypeptides include fragments of the extracellular domain that retain a desired biological activity. DNA sequences encoding soluble 2F1 polypeptides are encompassed by the present invention.
2F1 fragments, including soluble polypeptides, may be prepared by any of a number of conventional techniques. A desired DNA sequence may be chemically synthesized using known techniques. DNA fragments also may be produced by restriction endonuclease digestion of a full length cloned DNA sequence, and isolated by electrophoresis on agarose gels. Oligonucleotides that reconstruct the 5xe2x80x2 or 3xe2x80x2 end of a DNA fragment to a desired point may be synthesized. The oligonucleotides may contain a restriction endonuclease cleavage site upstream of the desired coding sequence and position an initiation codon (ATG) at the 5xe2x80x2 terminus of the coding sequence. Linkers containing restriction endonuclease cleavage site(s) may be employed to insert the desired DNA fragment into an expression vector. Alternatively, known mutagenesis techniques may be employed to insert a stop codon at a desired point, e.g., immediately downstream of the codon for the last amino acid of the extracellular domain.
As a further alternative, the well known polymerase chain reaction (PCR) procedure may be employed to isolate a DNA sequence encoding a desired protein fragment. Oligonucleotides that define the termini of the desired fragment are employed as primers in the reaction. PCR procedures are described, for example, in Saiki et al. (Science 239:487, 1988) and in Recombinant DNA Methodology, Wu et al. eds., Academic Press Inc., San Diego, 1989, pp 189-196.
Regarding the foregoing discussion of signal peptides and the various domains of the 2F1 proteins, the skilled artisan will recognize that the above-described boundaries of such regions of the proteins are approximate. For example, although computer programs that predict the site of cleavage of a signal peptide are available, cleavage can occur at sites other than those predicted. Further, it is recognized that a protein preparation can comprise a mixture of protein molecules having different N-terminal amino acids, due to cleavage of the signal peptide at more than one site. In addition, the exact boundaries of a transmembrane region may differ from that predicted by a computer program. Such forms of 2F1 that retain a desired biological activity are included among the 2F1 polypeptides of the present invention.
The present invention provides purified 2F1 polypeptides, both recombinant and non-recombinant. Variants and derivatives of native 2F1 proteins that retain a desired biological activity are also within the scope of the present invention. 2F1 variants may be obtained by mutations of nucleotide sequences coding for native 2F1 polypeptides. A 2F1 variant, as referred to herein, is a polypeptide substantially homologous to a native 2F1, but which has an amino acid sequence different from that of a native 2F1 because of one or more deletions, insertions or substitutions.
The variant amino acid sequence preferably is at least 80% identical to a native 2F1 amino acid sequence, most preferably at least 90% identical. The percent identity may be determined, for example, by comparing sequence information using the GAP computer program, version 6.0 described by Devereux et al. (Nuc. Acids Res. 12:387, 1984) and available from the University of Wisconsin Genetics Computer Group (UWGCG). The GAP program utilizes the alignment method of Needleman and Wunsch (J. Mol. Biol. 48:443, 1970), as revised by Smith and Waterman (Adv. Appl. Math 2:482, 1981). The preferred default parameters for the GAP program include: (1) a unary comparison matrix (containing a value of 1 for identities and 0 for non-identities) for nucleotides, and the weighted comparison matrix of Gribskov and Burgess, Nucl. Acids Res. 14:6745, 1986, as described by Schwartz and Dayhoff, eds., Atlas of Protein Sequence and Structure, National Biomedical Research Foundation, pp. 353-358, 1979; (2) a penalty of 3.0 for each gap and an additional 0.10 penalty for each symbol in each gap; and (3) no penalty for end gaps.
DNA encoding such variants is provided by the present invention as well. Such DNA sequences preferably are at least 80% identical to a native 2F1 DNA sequence, most preferably at least 90% identical. The percent identity may be determined using known computer programs, such as the above-described GAP program.
Alterations of the native amino acid sequence may be accomplished by any of a number of known techniques. Mutations can be introduced at particular loci by synthesizing oligonucleotides containing a mutant sequence, flanked by restriction sites enabling ligation to fragments of the native sequence. Following ligation, the resulting reconstructed sequence encodes an analog having the desired amino acid insertion, substitution, or deletion.
Alternatively, oligonucleotide-directed site-specific mutagenesis procedures can be employed to provide an altered gene having particular codons altered according to the substitution, deletion, or insertion required. Methods of making the alterations set forth above are disclosed by Walder et al. (Gene 42:133, 1986); Bauer et al. (Gene 37:73, 1985); Craik (BioTechniques, Jan. 12-19 1985, ); Smith et al. (Genetic Engineering: Principles and Methods, Plenum Press, 1981); Kunkel (Proc. Natl. Acad. Sci. USA 82:488, 1985); Kunkel et al. (Methods in Enzymol. 154:367, 1987); and U.S. Pat. Nos. 4,518,584 and 4,737,462.
Variants include conservatively substituted sequences, meaning that one or more amino acid residues of a native 2F1 is replaced by a different residue, but that the conservatively substituted 2F1 polypeptide retains a desired biological activity of the native protein. Examples of conservative substitutions include substitution of residues that do not alter the secondary or tertiary structure of the protein.
A given amino acid may be replaced by a residue having similar physiochemical characteristics. Examples of conservative substitutions include substitution of one aliphatic residue for another, such as Ile, Val, Leu, or Ala for one another, or substitutions of one polar residue for another, such as between Lys and Arg; Glu and Asp; or Gln and Asn. Other conservative substitutions, e.g., involving substitutions of entire regions having similar hydrophobicity characteristics, are well known.
2F1 proteins also may be modified to create 2F1 derivatives by forming covalent or aggregative conjugates with other chemical moieties, such as glycosyl groups, lipids, phosphate, acetyl groups and the like. Covalent derivatives of 2Fls may be prepared by linking the chemical moieties to functional groups on 2F1 amino acid side chains, or at the N-terminus or C-terminus of an 2F1 polypeptide or the extracellular domain thereof. Other derivatives of 2F1 within the scope of this invention include covalent or aggregative conjugates of 2F1s with other proteins or polypeptides, e.g., N-terminal or C-terminal fusions produced by recombinant DNA technology. For example, the conjugate may comprise a heterologous signal or leader polypeptide sequence at the N-terminus of a 2F1 polypeptide. The signal or leader peptide co-translationally or post-translationally directs transfer of the conjugate from its site of synthesis to a site inside or outside of the cell membrane or cell wall.
2F1 polypeptide fusions can comprise peptides added to facilitate purification and identification of 2F1. Such peptides include, for example, poly-His or the antigenic identification peptides described in U.S. Pat. No. 5,011,912 and in Hopp et al., Bio/Technology 6:1204, 1988. One such peptide is the FLAG(copyright) peptide, Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys (DYKDDDDK) (SEQ ID NO:5), which is highly antigenic and provides an epitope reversibly bound by a specific monoclonal antibody, enabling rapid assay and facile purification of expressed recombinant protein. Expression systems useful for fusing the Flag(copyright) octapeptide to the N- or C-terminus of a given protein are available from Eastman Kodak Co., Scientific Imaging Systems Division, New Haven, Conn., as are monoclonal antibodies that bind the octapeptide.
The present invention further includes 2F1 polypeptides with or without associated native-pattern glycosylation. 2F1 expressed in yeast or mammalian expression systems may be similar to or significantly different from a native 2F1 polypeptide in molecular weight and glycosylation pattern, depending upon the choice of expression system. Expression of 2F1 polypeptides in bacterial expression systems, such as E. coli, provides non-glycosylated molecules.
N-glycosylation sites in the 2F1 extracellular domain can be modified to preclude glycosylation. N-glycosylation sites in eukaryotic polypeptides are characterized by an amino acid triplet Asn-X-Y, wherein X is any amino acid except Pro and Y is Ser or Thr. The human 2F1 protein extracellular domain contains such triplets at amino acids 72-74, 83-85, 131-133, 149-151, 178-180, 184-186, 217-219, and 278-280 of SEQ ID NO:2. The murine 2F1 protein contains such triplets at amino acids 32-34, 53-55, 89-91, 93-95, 116-118, 171-173, 176-178, 182-184, 215-217, 277-279, and 460-462 of SEQ ID NO:4. Appropriate modifications to the nucleotide sequence encoding this triplet will result in substitutions, additions or deletions that prevent attachment of carbohydrate residues at the Asn side chain. Alteration of a single nucleotide, chosen so that Asn is replaced by a different amino acid, for example, is sufficient to inactivate an N-glycosylation site. Known procedures for inactivating N-glycosylation sites in proteins include those described in U.S. Pat. No. 5,071,972 and EP 276,846.
Additional variants are those in which cysteine residues that are not essential for biological activity are deleted or replaced with other amino acids, preventing formation of incorrect intramolecular disulfide bridges upon renaturation. As with the other IL-1R family members, the extracellular domain of 2F1 contains three immunoglobulin-like (Ig) domains. Based on alignment of the human 2F1 amino acid sequence with that of other family members, the cysteines predicted to form the typical intradomain disulfide bonds of the Ig domains are located at positions 121, 166, 218, and 279 of SEQ ID NO:2. The first (most N-terminal) Ig domain includes the first (residue 22) but lacks the second cysteine of the pair conserved in other proteins of this family. The first Ig domain of 2F1 thus is predicted to lack the intradomain disulfide bond that is typical of Ig domains. Like all IL-1R-like proteins except T1/ST2, mouse and human 2F1 also have a cysteine residue just a few residues C-terminal to the point of signal peptide cleavage (the cysteine at position 2 of of SEQ ID NO:2 and at position 4 of of SEQ ID NO:4). 2F1 fragments and variants preferably contain these conserved cysteines.
Other variants are prepared by modification of adjacent dibasic amino acid residues to enhance expression in yeast systems in which KEX2 protease activity is present. EP 212,914 discloses the use of site-specific mutagenesis to inactivate KEX2 protease processing sites in a protein. KEX2 protease processing sites are inactivated by deleting, adding or substituting residues to alter Arg-Arg, Arg-Lys, and Lys-Arg pairs to eliminate the occurrence of these adjacent basic residues. Human 2F1 contains such KEX2 protease processing sites at amino acids 94-95, 296-297, 345-346, 418-419, and 448-449 of SEQ ID NO:2. Murine 2F1 contains KEX2 protease processing sites at amino acids 87-88, 96-97, 231-232, 244-245, 295-296, 339-340, 416-417, 432-433, and 446-447 of SEQ ID NO:4. Lys-Lys pairings are considerably less susceptible to KEX2 cleavage, and conversion of Arg-Lys or Lys-Arg to Lys-Lys represents a conservative and preferred approach to inactivating KEX2 sites.
Naturally occurring 2F1 variants are also encompassed by the present invention. Examples of such variants are proteins that result from alternative MRNA splicing events or from proteolytic cleavage of the 2F1 protein, wherein a desired biological activity is retained. Alternative splicing of MRNA may yield a truncated but biologically active 2F1 protein, such as a naturally occurring soluble form of the protein, for example. Variations attributable to post-translational processing or proteolysis include, for example, differences in the N- or C-termini upon expression in different types of host cells, due to proteolytic removal of one or more terminal amino acids from the 2F1 protein (generally from 1-5 terminal amino acids).
2F1 proteins in which differences from the amino acid sequence of SEQ ID NO:2 are attributable to genetic polymorphism (allelic variation among individuals producing the protein) are also among the naturally occurring variants contemplated herein. The human 2F1 sequence presented in SEQ ID NO:1 is derived from three cDNA clones from a peripheral blood lymphocyte library and four PCR clones from the epidermal carcinoma line KB (see example 1). The codon for alanine 298 is polymorphic, being present in the PBL clones and two of the KB clones, and absent from the other two KB clones. It is also absent from the two mouse clones that were derived from an EL4 T cell library. The present invention thus provides human 2F1 proteins either containing or lacking an alanine residue at position 298.
The present invention provides isolated DNA sequences encoding the novel 2F1 polypeptides disclosed herein. 2F1-encoding DNA encompassed by the present invention includes, for example, cDNA, chemically synthesized DNA, DNA isolated by PCR, genomic DNA, and combinations thereof. Genomic 2F1 DNA may be isolated by conventional techniques, e.g., by using the DNA of SEQ ID NOS:1 or 3, or a fragment thereof, as a probe in a hybridization procedure.
Particular embodiments of the present invention are directed to an isolated DNA comprising nucleotides 1 to 1626 of SEQ ID NO:1 (the entire coding region), nucleotides 58 to 1626 of SEQ ID NO:1 (encoding mature human 2F1), nucleotides 381 to 1994 of SEQ ID NO:3 (the entire coding region), or nucleotides 435 to 1994 of SEQ ID NO:3 (encoding mature murine 2F1). In other embodiments, isolated DNA sequences encode a 2F1 fragment, such as one of the above-described soluble polypeptides. Such DNAs include a DNA comprising nucleotides 1 to 985 of SEQ ID NO:1 (which encode amino acids xe2x88x9219 to 310 of SEQ ID NO:2), nucleotides 58 to 985 of SEQ ID NO:1 (which encode amino acids 1 to 310 of SEQ ID NO:2), nucleotides 381 to 1355 of SEQ ID NO:3 (which encode amino acids xe2x88x9218 to 307 of SEQ ID NO:4), and nucleotides 435 to 1355 of SEQ ID NO:3 (which encode amino acids 1 to 307 of SEQ ID NO:4). DNAs encoding the various forms of 2F1 disclosed herein, e.g., 2F1 variants and fusion proteins, are encompassed by the present invention.
Nucleic acid sequences within the scope of the present invention include isolated DNA and RNA sequences that hybridize to the native 2F1 nucleotide sequences disclosed herein under moderately or highly stringent conditions, and which encode biologically active 2F1. Moderate stringency hybridization conditions refer to conditions described in, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual, 2 ed. Vol. 1, pp. 1.101-104, Cold Spring Harbor Laboratory Press, (1989). Conditions of moderate stringency, as defined by Sambrook et al., include use of a prewashing solution of 5xc3x97SSC, 0.5% SDS, 1.0 mnM EDTA (pH 8.0), hybridization at about 55xc2x0 C. in 5xc3x97SSC overnight, followed by washing at 50-55xc2x0 C. in 2xc3x97SSC, 0.1% SDS. Highly stringent conditions include higher temperatures of hybridization and washing. The skilled artisan will recognize that the temperature and wash solution salt concentration may be adjusted as necessary according to factors such as the length of the probe. In one embodiment, highly stringent conditions include hybridization at 68xc2x0 C. followed by washing in 0.1xc3x97SSC/0.1% SDS at 68xc2x0 C.
Due to the known degeneracy of the genetic code, wherein more than one codon can encode the same amino acid, a DNA sequence may vary from that presented in SEQ ID NO:1 or 3, and still encode an 2F1 protein having the amino acid sequence of SEQ ID NO:2 or 4, respectively. Such variant DNA sequences may result from silent mutations that occur during PCR amplification, for example. Alternatively, the variant sequence may be the product of deliberate mutagenesis of a native sequence.
The present invention thus provides isolated DNA sequences encoding biologically active 2F1, selected from: (a) DNA derived from the coding region of a native mammalian 2F1 gene (e.g., DNA comprising the coding region of the nucleotide sequence presented in SEQ ID NO:1 or 3); (b) DNA capable of hybridization to a DNA of (a) under moderately or highly stringent conditions; and (c) DNA which is degenerate as a result of the genetic code to a DNA defined in (a) or (b). The 2F1 proteins encoded by such DNA sequences are encompassed by the present invention.
Examples of 2F1 proteins encoded by DNA that varies from the native DNA sequence of SEQ ID NO:1 or 3, wherein the variant DNA will hybridize to the native DNA sequence under moderately or highly stringent conditions, include, but are not limited to, 2F1 fragments and 2F1 proteins comprising inactivated N-glycosylation site(s) or inactivated KEX2 protease processing site(s). Further examples are 2F1 proteins encoded by DNA derived from other mammalian species, wherein the DNA will hybridize to the human DNA of SEQ ID NO:1 or the mouse DNA of SEQ ID NO:3.
Purified 2F1 Protein and Uses Thereof
The present invention provides purified 2F1 polyeptides, which may be produced by recombinant expression systems as described below or purified from naturally occurring cells. Conventional protein purification techniques may be employed.
The desired degree of purity may depend on the intended use of the protein. A relatively high degree of purity is desired when the protein is to be administered in vivo, for example. Advantageously, 2F1 polypeptides are purified such that no protein bands corresponding to other (non-2F1) proteins are detected by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). It will be recognized by one skilled in the pertinent field that multiple bands corresponding to 2F1 protein may be detected by SDS-PAGE, due to differential glycosylation, variations in post-translational processing, and the like, as discussed above. Most preferably, 2F1 is purified to substantial homogeneity, as indicated by a single protein band upon analysis by SDS-PAGE. The protein band may be visualized by silver staining, Coomassie blue staining, or (if the protein is radiolabeled) by autoradiography.
One process for producing the 2F1 protein comprises culturing a host cell transformed with an expression vector comprising a DNA sequence that encodes 2F1 under conditions such that 2F1 is expressed. The 2F1 protein is then recovered from culture medium or cell extracts, depending upon the expression system employed. As the skilled artisan will recognize, procedures for purifying the recombinant 2F1 will vary according to such factors as the type of host cells employed and whether or not the 2F1 is secreted into the culture medium.
For example, when expression systems that secrete the recombinant protein are employed, the culture medium first may be concentrated using a commercially available protein concentration filter, for example, an Amicon or Millipore Pellicon ultrafiltration unit. Following the concentration step, the concentrate can be applied to a purification matrix such as a gel filtration medium. Alternatively, an anion exchange resin can be employed, for example, a matrix or substrate having pendant diethylaminoethyl (DEAE) groups. The matrices can be acrylamide, agarose, dextran, cellulose or other types commonly employed in protein purification. Alternatively, a cation exchange step can be employed. Suitable cation exchangers include various insoluble matrices comprising sulfopropyl or carboxymethyl groups. Sulfopropyl groups are preferred. Finally, one or more reversed-phase high performance liquid chromatography (RP-HPLC) steps employing hydrophobic RP-HPLC media, (e.g., silica gel having pendant methyl or other aliphatic groups) can be employed to further purify 2F1. Some or all of the foregoing purification steps, in various combinations, can be employed to provide a substantially homogeneous recombinant protein.
It is also possible to utilize an affinity column comprising an antibody that binds 2F1 to purify 2F1 polypeptides by immunoaffinity chromatography. Example 8 describes a procedure for employing the 2F1 protein of the present invention as an immunogen to generate monoclonal antibodies.
The foregoing chromatography procedures are among those that may be employed to purify either recombinant or non-recombinant 2F1. Recombinant cell culture enables the production of the protein free of those contaminating proteins that may be normally associated with 2F1 as it is found in nature, e.g., on the surface of certain cell types.
Recombinant protein produced in bacterial culture is usually isolated by initial disruption of the host cells, centrifugation, extraction from cell pellets if an insoluble polypeptide, or from the supernatant fluid if a soluble polypeptide, followed by one or more concentration, salting-out, ion exchange, affinity purification or size exclusion chromatography steps. Finally, RP-HPLC can be employed for final purification steps. Microbial cells can be disrupted by any convenient method, including freeze-thaw cycling, sonication, mechanical disruption, or use of cell lysing agents.
2F1 preferably is expressed as a secreted polypeptide to simplify purification. Secreted recombinant polypeptides from a yeast host cell fermentation can be purified by methods analogous to that disclosed by Urdal et al. (J. Chromatog. 296:171, 1984), which includes two sequential, reversed-phase HPLC steps.
Conjugates comprising a 2F1 polypeptide and a detectable agent are provided herein. The agent preferably is covalently bound to the 2F1 polypeptide. Such conjugates find use in in vitro assays, for example.
Suitable agents include, but are not limited to, radionuclides, chromophores, fluorescent compounds, enzymes that catalyze a colorimetric or fluorometric reaction, and the like, with the particular agent being chosen according to the intended application. Suitable radionuclides include, but are not limited to, 123I, 131I, 99mTc, 111In, and 76Br.
The agents may be attached to the 2F1 using any of the conventional methods by which such compounds are attached to polypeptides in general. Functional groups on amino acid side chains of an 2F1 may be reacted with functional groups on a desired agent to form covalent bonds, for example. The agent may be covalently linked to 2F1 via an amide bond, hindered disulfide bond, acid-cleavable linkage, and the like, which are among the linkages that may be chosen according to such factors as the structure of the desired agent. Alternatively, the 2F1 or the agent may be derivatized to generate or attach a desired reactive functional group. The derivatization may involve attachment of one of the bifunctional coupling reagents available for linking various molecules to proteins (Pierce Chemical Company, Rockford Ill.). A number of techniques for radiolabeling proteins are known. Radionuclide metals may be attached to 2F1 using a suitable bifunctional chelating agent, examples of which are described in U.S. Pat. No. 4,897,255 and 4,965,392.
As described in example 7, the signaling (cytoplasmic) domain of 2F1 transduces a biological signal that stimulates prostaglandin E2 synthesis. Prostaglandins are naturally occurring long-chain hydroxy fatty acids exhibiting biological effects that include, inter alia, mediating pain and inflammnation.
One embodiment of the present invention is directed to the use of soluble 2F1 polypeptides to inhibit prostaglandin synthesis. In vivo, signal transduction may be initiated by the the binding of unidentified ligand(s) to receptors comprising 2F1. Soluble 2F1 is administered to a mammal to bind such ligands, thereby inhibiting ligand binding to endogenous cell surface 2F1.
Soluble 2F1 polypeptides may be administered to a mammal to treat conditions that are mediated by a prostaglandin. A condition is said herein to be mediated by a prostaglandin when the condition is, at least in part, caused or exacerbated (directly or indirectly) by a prostaglandin.
Such conditions include, but are not limited to, inflammation associated with arthritis (especially rheumatoid arthritis and osteoarthritis), inflammation of the lungs associated with allergy or asthma, adult respiratory distress syndrome, inflammatory bowel disease, and inflammation resulting from injury (especially injury of a joint). The desirability of inhibiting prostaglandins to treat fever, Bartter""s syndrome, diabetes mellitus, patent ductus arteriosus, and dysmenorrhea is discussed in Harrisons""s Principles of Internal Medicine, 13th Edition, Vol. 1, Isselbacher et al., Eds., McGraw-Hill, Inc. New York, 1994, pp 433-435.
Prostaglandin E2 (PGE2) also has been implicated in bone resorption, including the bone resorption associated with rheumatoid arthritis and periodontal disease (Isselbacher et al., Eds., supra, at page 434). PGE2 has been reported to cause increased vascular permeability, which is an aspect of the inflammatory response that can lead to local edema (Isselbacher et al., Eds., supra, at page 435). Prostaglandins and their role in inflammation are discussed further in Pathophysiology: Clinical Concepts of Disease Processes, 3rd Edition, Price and Wilson, Eds., McGraw-Hill Book Company, New York, 1986, pp 36-38; and Inflammation: Basic Principles and Clinical Correlates, Second Edition, Galin et al., Eds., Raven Press, New York, 1992.
Prostaglandins have been suggested to play roles in modulating the immune response. PGE2 can suppress mitogen-induced stimulation of human lymphocytes, for example. Inhibition of PGE2 thus may be beneficial in patients in which depressed cellular immunity is attributable, at least in part, to the action of prostaglandins. (See Isselbacher et al., Eds., supra, at page 435). Roles for PGE1 and PGE2 in angiogenesis have also been suggested.
It is notable that the 2F1 signaling domain transduced a signal that resulted in activation of the transcription factor NF-xcexaB (see example 5). The anti-inflammatory effect of certain drugs (glucocorticoids) is believed to be attributable, at least in part, to inhibition of NF-xcexaB activation (Auphan et al., Science 270:286-290, 1995; Marx, Science 270:232-233, 1995). Soluble 2F1 polypeptides thus may be used to inhibit NF-xcexaB activation signals transduced via 2F1.
NF-xcexaB activation has been linked to TNF-induced replication of human immunodeficiency virus (HIV) in infected cells, including T cells (Howard et al., Proc. Natl. Acad. Sci. USA 90:2335-2339, 1993). 2F1 is expressed on T-cells, and an NF-xcexaB activation signal is transduced by the 2F1 signaling domain. Thus, soluble 2F1 may be employed to reduce HIV expression in HIV-infected cells. An effective amount of soluble 2F1 is administered in vivo to inhibit NF-xcexaB activation that results from signaling through 2F1. Any HIV replication that would have resulted from such NF-xcexaB activation is thus diminished.
Oligomeric Forms of 2F1
Encompassed by the present invention are oligomers, such as dimers, trimers, or higher oligomers, that contain 2F1. Such oligomers may be naturally occurinc or produced by means such as recombinant DNA technology.
The 2F1 moieties of the oligomer may be soluble 2F1 polypeptides. In certain embodiments, the oligomers comprise from two to four 2F1 polypeptides.
Oligomers may be formed by disulfide bonds between cysteine residues on different 2F1 polypeptides, or by non-covalent interactions between 2F1 polypeptide chains, for example. In other embodiments, oligomers comprise multiple 2F1 polypeptides joined via covalent or non-covalent interactions between peptide moieties fused to the 2F1 polypeptides. Such peptides may be peptide linkers (spacers), or peptides that have the property of promoting oligomerization. Leucine zippers and certain polypeptides derived from antibodies are among the peptides that can promote oligomerization of 2F1 polypeptides attached thereto, as described in more detail below.
Preparation of fusion proteins comprising heterologous polypeptides fused to various portions of antibody-derived polypeptides (including the Fc domain) has been described, e.g., by Ashkenazi et al., (PNAS USA 88:10535, 1991); Byrn et al., (Nature 344:677, 1990); and Hollenbaugh and Aruffo (xe2x80x9cConstruction of Immunoglobulin Fusion Proteinsxe2x80x9d, in Current Protocols in Immunology, Suppl. 4, pages 10.19.1-10.19.11, 1992). In one embodiment of the invention, a 2F1 dimer is created by fusing a 2F1 to the Fc region of an antibody (IgGI). The Fc polypeptide preferably is fused to the C-terminus of a soluble 2F1. A gene fusion encoding the 2F1/ Fc fusion protein is inserted into an appropriate expression vector. The 2F1/Fc fusion proteins are expressed in host cells transformed with the recombinant expression vector and allowed to assemble much like antibody molecules, whereupon interchain disulfide bonds form between Fc polypeptides to yield divalent 2F1. The desired dimer may be recovered by conventional procedures, e.g., by affinity chromatography employing a protein A or protein G column that will bind the Fc moieties.
The term xe2x80x9cFc polypeptidexe2x80x9d as used herein includes native and mutein forms of polypeptides derived from the Fc region of an antibody. Truncated forms of such polypeptides containing the hinge region that promotes dimerization are also included. One suitable Fc polypeptide is described in PCT application WO 93/10151, hereby incorporated by reference. This Fc polypeptide is a single chain polypeptide extending from the N-terminal hinge region to the native C-terminus (i.e., is an essentially full ength antibody Fc region). Another useful Fc polypeptide is described in U.S. Pat. No. 5,457,035. The amino acid sequence of the mutein is identical to that of the native Fc sequence presented in WO 93/10151, except that amino acid 19 has been changed from Leu to Ala, amino acid 20 has been changed from Leu to Glu, and amino acid 22 has been changed from Gly to Ala. This mutein Fc exhibits reduced affinity for Fc receptors. Procedures for preparing a fusion protein containing an Fc or Fc mutein polypeptide are described further in Baum et al. (EMBO J. 13:3992-4001, 1994).
In other embodiments, 2F1 may be substituted for the variable portion of an antibody heavy or light chain. If fusion proteins are made with both heavy and light chains of an antibody, it is possible to form an 2F1 oligomer with as many as four 2F1 extracellular regions.
Another method for preparing oligomeric 2F1 involves use of a leucine zipper. Leucine zipper domains are peptides that promote oligomerization of the proteins in which they are found. Originally identified in several DNA-binding proteins (Landschulz et al., Science 240:1759, 1988), leucine zippers have since been found in a variety of different proteins. Among the known leucine zippers are naturally occurring peptides and derivatives thereof that dimerize or trimerize. Examples of leucine zipper domains suitable for producing soluble oligomeric proteins are those described in PCT application WO 94/10308. Peptides that preferentially form trimers include, for example, the leucine zipper derived from lung surfactant protein D (SPD) described in Hoppe et al. (FEBS Letters 344:191, 1994), and U.S. patent application Ser. No. 08/446,922, hereby incorporated by reference. Recombinant fusion proteins comprising a soluble 2F1 polypeptide fused to a leucine zipper peptide are expressed in suitable host cells, and the resulting soluble oligomeric 2F1 that forms is recovered from the culture supernatant.
As a further alternative, oligomeric 2F1 may be expressed as a recombinant fusion protein, with or without peptide linkers between the 2F1 moieties. Suitable peptide linkers are known in the art, and may be employed according to conventional techniques. Among the suitable peptide linkers are those described in U.S. Pat. Nos. 4,751,180 and 4,935,233, which are hereby incorporated by reference. A DNA sequence encoding a desired peptide linker may be inserted between, and in the same reading frame as, the DNA sequences encoding 2F1, using any suitable conventional technique. In one embodiment, two soluble 2F1 polypeptides are joined by a peptide linker.
The above-described oligomers may be purified by conventional protein purification procedures. Immunoaffinity chromatography using an antibody directed against 2F1 may be employed, for example. Oligomers containing antibody-derived Fc polypeptides may be purified by affinity chromatography, employing a protein A or protein G column that will bind the Fc moieties.
The present invention provides isolated DNA sequences encoding 2F1 polypeptides fused to immunoglobin-derived polypeptides. Such DNA sequences may encode a soluble 2F1 fused to an antibody Fc region polypeptide, for example. DNA sequences encoding fusion proteins comprising multiple 2F1 polypeptide moieties are also encompassed by the present invention.
Compositions Comprising 2F1
The present invention provides compositions (including pharmaceutical compositions) comprising an effective amount of a purified 2F1 polypeptide and a suitable diluent, excipient, or carrier. 2F1 polypeptides administered in vivo preferably are in the form of a pharmaceutical composition.
The compositions of the present invention may contain a 2F1 protein in any form described herein, including oligomers, variants, derivatives, and biologically active fragments. In one embodiment of the invention, the composition comprises a soluble human 2F1 protein.
2F1 proteins may be formulated according to known methods that are used to prepare pharmaceutically useful compositions. Components that are commonly employed in pharmaceutical formulations include those described in Remington""s Pharmaceutical Sciences, 16th ed., 1980, Mack Publishing Company.
2F1 protein employed in a pharmaceutical composition preferably is purified such that the 2F1 protein is substantially free of other proteins of natural or endogenous origin, desirably containing less than about 1% by mass of protein contaminants residual of production processes. Such compositions, however, can contain other proteins added as stabilizers, carriers, excipients or co-therapeutics.
Components of the compositions will be nontoxic to patients at the dosages and concentrations employed. Ordinarily, the preparation of such compositions entails combining a mammalian 2F1 polypeptide or derivative thereof with buffers, antioxidants such as ascorbic acid, low molecular weight (less than about 10 residues) peptides, proteins, amino acids, carbohydrates including glucose, sucrose, or dextrans, chelating agents such as EDTA, glutathione, or other stabilizers and excipients. Neutral buffered saline is one appropriate diluent.
For therapeutic use, the compositions are administered in a manner and dosage appropriate to the indication and the patient. Administration may be by any suitable route, including but not limited to continuous infusion, local administration, sustained release from implants (gels, membranes, and the like), or intravenous injection.
Antibodies that Specifically Bind 2F1
The 2F1 proteins of the present invention, or immunogenic fragments thereof, may be employed in generating antibodies. The present invention thus provides antibodies that specifically bind 2F1, i.e., the antibodies bind to 2F1 via the antigen-binding sites of the antibody (as opposed to non-specific binding).
Polyclonal and monoclonal antibodies may be prepared by conventional techniques. See, for example, Monoclonal Antibodies, Hybridomas: A New Dimension in Biological Analyses, Kennet et al. (eds.), Plenum Press, New York (1980); and Antibodies: A Laboratory Manual, Harlow and Land (eds.), Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., (1988). Production of monoclonal antibodies that are immunoreactive with 2F1 is further illustrated in example 8 below.
Antigen-binding fragments of such antibodies, which may be produced using conventional techniques, are also encompassed by the present invention. Examples of such fragments include, but are not limited to, Fab, F(abxe2x80x2), and F(abxe2x80x2)2 fragments. Antibody fragments and derivatives produced by genetic engineering techniques are also provided.
The monoclonal antibodies of the present invention include chimeric antibodies, e.g., humanized versions of murine monoclonal antibodies. Such humanized antibodies may be prepared by known techniques, and offer the advantage of reduced immunogenicity when the antibodies are administered to humans. In one embodiment, a humanized monoclonal antibody comprises the variable region of a murine antibody (or just the antigen binding site thereof) and a constant region derived from a human antibody. Alternatively, a humanized antibody fragment may comprise the antigen binding site of a murine monoclonal antibody and a variable region fragment (lacking the antigen-binding site) derived from a human antibody. Procedures for the production of chimeric and further engineered monoclonal antibodies include those described in Riechmann et al. (Nature 332:323, 1988), Liu et al. (PNAS 84:3439, 1987), Larrick et al. (Bio/Technology 7:934, 1989), and Winter and Harris (TIPS 14:139, May, 1993).
Among the uses of the antibodies is use in assays to detect the presence of 2F1 polypeptides, either in vitro or in vivo. The antibodies find further use in purifying 2F1 by immunoaffinity chromatography. Those antibodies that additionally can block transduction of a biological signal through 2F1 may be used to inhibit a biological activity mediated by uch signal transduction. Disorders mediated or exacerbated (directly or indirectly) by ignaling through 2F1 are thus treated. A therapeutic method involves in vivo administration of an amount of such an antibody that is effective in inhibiting an undesired 2F1-mediated biological activity. Such antibodies may be administered to inhibit prostaglandin synthesis, thereby treating one of the above-described prostaglandin-mediated disorders, for example.
Pharmaceutical compositions comprising an antibody that is directed against 2F1, and a suitable, diluent, excipient, or carrier, are provided herein. Suitable components of such compositions are as described above for compositions containing 2F1 proteins.
Conjugates comprising a diagnostic (detectable) or therapeutic agent attached to the above-described antibodies are provided herein. In one embodiment, the agent is a radionuclide or drug. Techniques for attaching such agents to antibodies are well known.
Expression Systems
The present invention provides recombinant expression vectors for expression of 2F1, and host cells transformed with the expression vectors. Any suitable expression system may be employed. The vectors include an 2F1 DNA sequence operably linked to suitable transcriptional or translational regulatory nucleotide sequences, such as those derived from a mammalian, microbial, viral, or insect gene. Examples of regulatory sequences include transcriptional promoters, operators, or enhancers, an mRNA ribosomal binding site, and appropriate sequences which control transcription and translation initiation and termination. Nucleotide sequences are operably linked when the regulatory sequence functionally relates to the 2F1 DNA sequence. Thus, a promoter is operably linked to an 2F1 DNA sequence if the promoter controls the transcription of the 2F1 DNA sequence. An origin of replication, which confers the ability to replicate in the desired host cells, and a selection gene by which transformants are identified, are generally incorporated into the expression vector.
In addition, sequences encoding appropriate signal peptides that are not native to the 2F1 gene can be incorporated into expression vectors. For example, a DNA sequence for a signal peptide (secretory leader) may be fused in frame to the 5xe2x80x2 end of an 2F1 sequence. A signal peptide that is functional in the intended host cells enhances extracellular secretion of the 2F1 polypeptide. The signal peptide is cleaved from the 2F1 polypeptide upon secretion of 2F1 from the cell.
Suitable host cells for expression of 2F1 polypeptides include prokaryotes, yeast or higher eukaryotic cells. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts are described, for example, in Pouwels et al. Cloning Vectors: A Laboratory Manual, Elsevier, New York, (1985). Cell-free ranslation systems could also be employed to produce 2F1 polypeptides using RNAs derived from DNA constructs disclosed herein.
Prokaryotes include gram negative or gram positive organisms, for example, E. coli or Bacilli. Suitable prokaryotic host cells for transformation include, for example, E. coli, Bacillus subtilis, Salmonella typhimuirium, and various other species within the genera Pseudomonas, Streptomyces, and Staphylococcus. In a prokaryotic host cell, such as E. col, an 2F1 polypeptide may include an N-terminal methionine residue to facilitate expression of the recombinant polypeptide in the prokaryotic host cell. The N-terminal Met may be cleaved from the expressed recombinant 2F1 polypeptide.
Expression vectors for use in prokaryotic host cells generally comprise one or more phenotypic selectable marker genes. A phenotypic selectable marker gene is, for example, a gene encoding a protein that confers antibiotic resistance or that supplies an autotrophic requirement. Examples of useful expression vectors for prokaryotic host cells include those derived from commercially available plasmids such as the cloning vector pBR322 (ATCC 37017). pBR322 contains genes for ampicillin and tetracycline resistance and thus provides simple means for identifying transformed cells. An appropriate promoter and an 2F1 DNA sequence are inserted into the pBR322 vector.
Promoter sequences commonly used for recombinant prokaryotic host cell expression vectors include xcex2-lactamase (penicillinase), lactose promoter system (Chang et al., Nature 275:615, 1978; and Goeddel et al., Nature 281:544, 1979), tryptophan (trp) promoter system (Goeddel et al., Nucl. Acids Res. 8:4057, 1980; and EP-A-36776) and tac promoter (Maniatis, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, p. 412, 1982). A particularly useful prokaryotic host cell expression system employs a phage xcex PL promoter and a cI857ts thermolabile repressor sequence. Plasmid vectors available from the American Type Culture Collection which incorporate derivatives of the xcex PL promoter include plasmid pHUB2 (resident in E. coli strain JMB9 (ATCC 37092)) and pPLc28 (resident in E. coli RR1 (ATCC 53082)).
2F1 alternatively may be expressed in yeast host cells, preferably from the Saccharomyces genus (e.g., S. cerevisiae). Other genera of yeast, such as Pichia or Kluyveromyces, may also be employed. Yeast vectors will often contain an origin of replication sequence from a 2xcexc yeast plasmid, an autonomously replicating sequence (ARS), a promoter region, sequences for polyadenylation, sequences for transcription termination, and a selectable marker gene.
Suitable promoter sequences for yeast vectors include, among others, promoters for metallothionein, 3-phosphoglycerate kinase (Hitzeman et al., J. BioL Chem. 255:2073, 1980) or other glycolytic enzymes (Hess et al., J. Adv. Enzyme Reg. 7:149, 1968; and Holland et al., Biochem. 17:4900, 1978), such as enolase, glyceraldehyde-3-phosphate dehydrogenase, hexokinase, pyruvate decarboxylase, phosphofructokinase, glucose-6-phosphate isomerase, 3-phosphoglycerate mutase, pyruvate kinase, triosephosphate isomerase, phosphoglucose isomerase, and glucokinase. Other suitable vectors and promoters for use in yeast expression are further described in Hitzeman, EPA-73,657. Another alternative is the glucose-repressible ADH2 promoter described by Russell et al. (J. Biol. Chem. 258:2674, 1982) and Beier et al. (Nature 300:724, 1982). Shuttle vectors replicable in both yeast and E. coli may be constructed by inserting DNA sequences from pBR322 for selection and replication in E. coli (Ampr gene and origin of replication) into the above-described yeast vectors.
The yeast xcex1-factor leader sequence may be employed to direct secretion of the 2F1 polypeptide. The xcex1-factor leader sequence is inserted between the promoter sequence and the structural gene sequence. See, e.g., Kurjan et al., Cell 30:933, 1982; Bitter et al., Proc. Natl. Acad. Sci. USA 81:5330, 1984; U. S. Pat. No. 4,546,082; and EP 324,274. Other leader sequences suitable for facilitating secretion of recombinant polypeptides from yeast hosts are known to those of skill in the art. A leader sequence may be modified near its 3xe2x80x2 end to contain one or more restriction sites. This will facilitate fusion of the leader sequence to the structural gene.
Yeast transformation protocols are known to those of skill in the art. One such protocol is described by Hinnen et al., Proc. Natl. Acad. Sci. USA 75:1929, 1978. The Hinnen et al. protocol selects for Trp+ transformants in a selective medium, wherein the selective medium consists of 0.67% yeast nitrogen base, 0.5% casamino acids, 2% glucose, 10 xcexcg/ml adenine and 20 xcexcg/ml uracil.
Yeast host cells transformed by vectors containing ADH2 promoter sequence may be grown for inducing expression in a xe2x80x9crichxe2x80x9d medium. An example of a rich medium is one consisting of 1% yeast extract, 2% peptone, and 1% glucose supplemented with 80 xcexcg/ml adenine and 80 xcexcg/ml uracil. Derepression of the ADH2 promoter occurs when glucose is exhausted from the medium.
Mammalian or insect host cell culture systems could also be employed to express recombinant 2F1 polypeptides. Baculovirus systems for production of heterologous proteins in insect cells are reviewed by Luckow and Summers, Bio/Technology 6:47 (1988). Established cell lines of mammalian origin also may be employed. Examples of suitable mammalian host cell lines include COS cells derived from monkey kidney cells (e.g., the COS-1 cell line ATCC CRL 1650, or the COS-7 line ATCC CRL 1651, Gluzman et al., Cell 23:175, 1981), L cells, C127 cells, 3T3 cells (ATCC CCL 163), Chinese hamster ovary (CHO) cells, HeLa cells, and BHK (ATCC CRL 10) cell lines, and the CV-1/EBNA-1 cell line derived from the African green monkey kidney cell line CVI (ATCC CCL 70) as described by McMahan et al. (EMBO J. 10: 2821, 1991).
Transcriptional and translational control sequences for mammalian host cell expression vectors may be excised from viral genomes. Commonly used promoter sequences and enhancer sequences are derived from Polyoma virus, Adenovirus 2, Simian Virus 40 (SV40), and human cytomegalovirus. DNA sequences derived from the SV40 viral genome, for example, SV40 origin, early and late promoter, enhancer, splice, and polyadenylation sites may be used to provide other genetic elements for expression of a structural gene sequence in a mammalian host cell. Viral early and late promoters are particularly useful because both are easily obtained from a viral genome as a fragment which may also contain a viral origin of replication (Fiers et al., Nature 273:113, 1978). Smaller or larger SV40 fragments may also be used, provided the approximately 250 bp sequence extending from the Hind III site toward the Bgl I site located in the SV40 viral origin of replication site is included.
Expression vectors for use in mammalian host cells can be constructed as disclosed by Okayama and Berg (Mol. Cell. Biol. 3:280, 1983). A useful system for stable high level expression of mammalian cDNAs in C127 murine mammary epithelial cells can be constructed substantially as described by Cosman et al. (Mol. Immunol. 23:935, 1986). A useful high expression vector, PMLSV N1/N4, described by Cosman et al. (Nature 312:768, 1984) has been deposited as ATCC 39890. Additional mammalian expression vectors are pDC406 (McMahan et al., EMBO J. 10:2821, 1991); HAV-EO (Dower et al., J. Immunol. 142:4314, 1989); pDC201 (Sims et al., Science 241:585, 1988); pDC302 (Mosley et al., Cell, 59:335, 1989); and those described in U.S. Pat. No. 5,350,683. Other suitable vectors may be derived from retroviruses.
In place of the native signal sequence, a heterologous signal sequence may be added, such as the signal sequence for interleukin-7 (IL-7) described in U.S. Pat. No. 4,965,195; the signal sequence for interleukin-2 receptor described in Cosman et al., Nature 312:768 (1984); the interleukin-4 receptor signal peptide described in EP 367,566; the type I interleukin-1 receptor signal peptide described in U.S. Pat. No. 4,968,607; and the type II interleukin-1 receptor signal peptide described in EP 460,846.
Nucleic Acids and Uses Thereof
The 2F1-encoding DNAs disclosed herein find use in the production of 2F1 polypeptides, as discussed above. DNA and RNA complements of the DNA presented in SEQ ID NOS:1 and 3 are provided herein, along with both single-stranded and double-stranded forms thereof. Fragments of the 2F1 nucleotide sequences presented herein are also useful. Such fragments desirably comprise at least about 17 contigous nucleotides of the sequence presented in SEQ ID NO:1 or SEQ ID NO:3, or the complement thereof.
Among the uses of such 2F1 nucleic acids (including fragments) is use as a probe. Such probes may be employed in cross-species hybridization procedures to isolate 2F1 DNA from additional mammalian species. As one example, a probe corresponding to the extracellular domain of 2F1 may be employed. The probes also find use in detecting the presence of 2F1 nucleic acids in in vitro assays and in such procedures as Northern and Southern blots. Cell types expressing 2F1 can be identified. Such procedures are well known, and the skilled artisan can choose a probe of suitable length, depending on the particular intended application. The probes may be labeled (e.g., with 32P) by conventional techniques.
2F1 nucleic acid fragments also find use as primers in polymerase chain reactions (PCR). 5xe2x80x2 and 3xe2x80x2 primers corresponding to the termini of a desired 2F1 DNA may be employed in isolating and amplifying the DNA, using conventional PCR techniques.
Other useful fragments of the 2F1 nucleic acids are antisense or sense oligonucleotides comprising a single-stranded nucleic acid sequence (either RNA or DNA) capable of binding to target 2F1 mRNA (sense) or 2F1 DNA (antisense) sequences. Antisense or sense oligonucleotides, according to the present invention, comprise a fragment of the coding region of 2F1 cDNA. Such a fragment generally comprises at least about 14 nucleotides, preferably from about 14 to about 30 nucleotides. The ability to create an antisense or a sense oligonucleotide based upon a cDNA sequence for a given protein is described in, for example, Stein and Cohen, Cancer Res. 48:2659, 1988 and van der Krol et al., BioTechniques 6:958, 1988.
Binding of antisense or sense oligonucleotides to target nucleic acid sequences results in the formation of duplexes that block translation (RNA) or transcription (DNA) by one of several means, including enhanced degradation of the duplexes, premature termination of transcription or translation, or by other means. The antisense oligonucleotides thus may be used to block expression of 2F1 proteins.
Antisense or sense oligonucleotides further comprise oligonucleotides having modified sugar-phosphodiester backbones (or other sugar linkages, such as those described in WO91/06629) and wherein such sugar linkages are resistant to endogenous nucleases. Such oligonucleotides with resistant sugar linkages are stable in vivo (i.e., capable of resisting enzymatic degradation) but retain sequence specificity to be able to bind to target nucleotide sequences. Other examples of sense or antisense oligonucleotides include those oligonucleotides which are covalently linked to organic moieties, such as those described in WO 90/10448, and other moieties that increase affinity of the oligonucleotide for a target nucleic acid sequence, such as poly-(L-lysine). Further still, intercalating agents, such as ellipticine, and alkylating agents or metal complexes may be attached to sense or antisense oligonucleotides to modify binding specificities of the antisense or sense oligonucleotide for the target nucleotide sequence.
Antisense or sense oligonucleotides may be introduced into a cell containing the target nucleic acid sequence by any gene transfer method, including, for example, CaPO4-mediated DNA transfection, electroporation, or by using gene transfer vectors such as Epstein-Barr virus. Antisense or sense oligonucleotides are preferably introduced into a cell containing the target nucleic acid sequence by insertion of the antisense or sense oligonucleotide into a suitable retroviral vector, then contacting the cell with the retroviral vector containing the inserted sequence, either iti vivo or ex vivo. Suitable retroviral vectors include, but are not limited to, those derived from the murine retrovirus M-MuLV, N2 (a retrovirus derived from M-MuLV), or the double copy vectors designated DCT5A, DCT5B and DCT5C (see PCT Application WO 90/13641).
Sense or antisense oligonucleotides also may be introduced into a cell containing the target nucleotide sequence by formation of a conjugate with a ligand binding molecule, as described in WO 91/04753. Suitable ligand binding molecules include, but are not limited to, cell surface receptors, growth factors, other cytokines, or other ligands that bind to cell surface receptors.
Alternatively, a sense or an antisense oligonucleotide may be introduced into a cell containing the target nucleic acid sequence by formation of an oligonucleotide-lipid complex, as described in WO 90/10448. The sense or antisense oligonucleotide-lipid complex is preferably dissociated within the cell by an endogenous lipase.